Double solvent extraction of tar acids



Sept 17, 19.57 M. B. NEuwoRTH 2,806,886

DOUBLE soLvENT EXTRACTION oF TAR ACIDS Filed 0G19'. 7, 1955 NNMLONI I-NVENTOR Patented Sept. 1.7,' 1957 United States Patent filCC DOUBLE SOLVENT EX'RACTIN 0F TAR ACIDS lllarlinA Neuworth, Pittsburgh, Pa., assigner to Pittsburgll Consolidation Coal Company, Pittsburgh, Pa.,

a'corporation of Pennsylvania Application October 7, 1955, Ser-iai No. 539,168

13 Claims. (Cl. 1260-627) This invention relates to the separation of organic compounds andmore particularly to the double solvent extraction of' dihydric phenols from a liquid mixture consisting essentially of high boiling monohydric and dihydric phenols.

Primarily, this invention is directed to the removal of color producing compounds found in the high boiling tar acidY .product resulting from the low temperature carbonization of coal, but this invention is equally applicable to the selective solvent extraction of dihydric phenols from any liquid mixture consisting essentially of high boiling monohydric phenols and dihydric phenols. This invention also is directed to the rening of tar acid oil and the separation and recovery of de-pinked tar acids from the tar acid oil.

Tar acids may be defined as phenols which are present in tar or tar distillates and are extractable with caustic soda solution.V Tar acids do not consist so much of phenol itself as of homologues of the series such as crgesols, xylenols and more complex phenol derivatives. The high boiling tar acids are the fraction boiling above 230 C. and are composed of both monohydric phenols and dihydric phenols. Some of the typical monohydric phenols are methyl ethyl phenol, polymethyl phenols, diethyl phenol and naphthol. Some of the typical dihydric phenols are pyrocatechol, resorcinol, hydroquinone and their alkylated derivatives. Throughout this specilication the term high boiling tar acids will designate those tar acids boiling above about 230 C. and low boiling tar acids will designate those boiling below 230 C.

One of the outlets `for high boiling tar acids is in the preparation of tar acid mixtures in an alkaline emulsion form for use as disinfectants. A factor that limits the marketability of the high boiling tar acids as disinfectants is the pink color of the alkaline emulsion which develops when the emulsion is exposed to air. It has been found that the coloring or pinking properties of the high boiling tar acids is due to the presence of various dihydric phenols in the emulsion. The removal oi the dihydric phenols, or the elimination of the color producing properties of the high boiling tar acids is called de-pinlzing.

lt is therefor the primary object of this invention to provide a process for de-pinking or removing the colorproducing compound from the tar acids in a continuous solvent extraction process.

A further object of this invention is to provide a method rof recovering the de-pinked tar acids from the solvent and recycling the solvent. Another object of this invention is to provide a process for removing dihydric phenols by solvent extraction from a mixture ci high boiling monohydric phenols and dihydric phenols in a continuous process. Another object of this invention is to provide aprocess for rehning tar acid oil and recovering de-pinked high boiling tar acids from the tar acid oil in a continuous process.

Many methods have been proposed for either de-pinlcing tar acids or removing dihydric phenols from a mixture of monohydricphenols and dihydric phenols. VThe prior methods, however, are unsatisfactory for various reasons. Some methods, such as the air blowing treatment of tar acids, destroy valuable monohydric phenols along with the color-producing dihydric phenols. Other methods, such as therwater extraction treatment of tar acids, only partially remove the color producing dihydric phenols and hence do not satisfactorily de-pink the tar acids. The chemical treatment of tar acids withnsodium tetraborate, buler agents and the like lare expensive to operate and require elaborate process equipment.V

ln accordance with my invention I have discovered that by contacting the tar acids with a paraiiinic naphtha solvent and an aqueous methanol solvent the color producing dihydric phenols may be separated from the high boiling tar acids. The color producing dihydric phenols are removed as extracts in the aqueous methanol phase while the de-pinked tar acids are removed in the paraflinic naphtha phase.

More speciiically, the tar acids are fed into a double solvent countercurrent extraction column at a point-between the two solvent feed points. Since the highy boiling tar acids have a high viscosity at room temperature, they may be treated to lower their viscosity before entering the extraction column. Any conventional method of lowering the viscosity of the high boiling tar acids may be used, however, l prefer to dissolve the tar acid feedstock in a naphtha solvent to lower its viscosity. As the tar acids are fed into the extraction column aqueous methanol is fed into the top portion ofthe extraction column and a naphtha solvent is fed into the bottom of the column. The tar acids are contacted with both the aqueous methanol and the naphtha solvent which pass through the column in countercurrent relation. The aqueous methanol strips out the color-producing dihydric phenols which are removed in the aqueous methanol solution from the bottom of the column; the' de-pinked tar acids dissolve in the naphtha solvent and-are removed in the naphtha solution from the top of the column.

At atmospheric pressure and normal temperature the aqueous methanol solvent shouldy contain about 30 to 40 percent by weight methanol. I have discovered that at these conditions of temperature and pressure, an aqueous methanol solution containing either less than 30 percent methanol or more than 40 percent methanol result in the formation of three liquid phases. The composition of the three phases formed is not known, however, their formati-on prevents the extraction type of separation.

The results of this invention are surprising inview of the results obtained and disclosed in U. S. VPatent 2,666,796 of whichl am a copatentee, wherein a process is described for extracting tar acids from neutral oils by solvent extraction using as solvents parainic naphtha and aqueous methanol of 55 to 75 percentconcentration. As shown in this patent, the naphtha rainate contains the neutral oils and the aqueous methanol extract contains the tar acids. Now Ihave discovered bychanging the concentration of the aqueous methanol solvent, the monohydric tar acids which are rejected from the naphtha phase in the above mentioned patent process, can be dissolved in the naphtha solvent.

For the naphtha solvent I prefer to vuse a parai'nic distillate obtained'from petroleum. The naphtha density should be less than 0.80 and preferably less than 0.75 to insure suicient gravity diiference between the two phases .in the extraction column to-eiect a ready separation of the phases. The hexane cut of a paraiinic distillate combinesall these critical properties and accordingly is preferred as the solvent in this invention. q v

For a clear understanding ofmy invention, its objects and advantages,.reference should be had to the following detailed description and accompanying drawing which .column 14.. Vstorage' tank 24 through a pipeline 26 into the bottom zation of bituminous coal to produce a neutral oil product, a low boiling tar acids product, a de-pinked high boiling tar acid product and a dihydric phenol product.

Referring to the drawing, tar acid oil is pumped from a storage tank continuously through a pipeline 12 into the central portion of a continuous countercurrent double solvent center feed extraction column 14.V The extraction column may be of an convenient designcapable of providing a suiiicient number of theoretical extraction stages to effect the desiredsseparation ofrtar acids from the tar acid soil. A conventional packed tower may be used, for example, as well as a pierced plate column, a bubble cap column, a rotating disc column or a column Ycontaining alternate zones of quiescence and turbulence.

Aqueous methanol solution is fed continuously from a methanol storage tank 16 through a pipeline 18 into the top of the extraction column 14. A mixing valve 20 is 'Ypositioned in the line 1S and water enters the mixing valve 20 through a pipeline 22. The mixing vvalve 2t) regulates the concentration of aqueous methanol so that an aqueous methanol solution containing from 55 to 75 percent by weight of methanol Venters the extraction Naphtha is fed continuously hom a naphtha of the extraction column 14.

Since the density of the aqueous methanol solution exceeds the density of the naphtha, the'aqueous methanol solution descends through the column and dissolves tar :acids while the lighter naphtha passes countercurrently upward through the column and dissolves the neutral oils contained in the tar acid oil feed.

Aqueous methanol extract containing purified recovered tar acids, is withdrawn continuously from the bottom of the extraction column 14 through a pipeline 2S and fed into a stripper or distillation column 3l).

The tar acids and Water solution leave the stripper 3l! and pass through a cooler 32 which aids in the phase separation of the Water from the tar acids. The tar acid and water mixture leaves the cooler 32 through a pipeline 34 and enters a phase separation tank 36. The puritied tar acids leave the separation tank 36 through a pipeline 38 and enter a fractionation column dll.

Anhydrous methanol passes overhead from the stripper through pipeline 42 to a reux condenser 44 and passes through a pipeline 46 to the aqueous methanol storage tank 16. A portion of the condensed Ymethanol Vmay be returned through a pipeline 4S to the top of the stripper 30 as reux.

Naphtha with dissolved neutral oil leaves the top of the extraction column 14 through a pipeline 59 and passes to a distillation column or stripper 52 where the naphtha is separated from the neutral oil. Naphtha passes overhead from the stripper 52 through arpipeline 54 and reflux condenser 56. A portion of the naphtha lmay be recirculated through a pipeline 5S as reiiux for the stripper S2. The naphtha leaves the reliux condenser 56 and returns through a pipeline 6i? to the naphtha storage tank 24. The neutral oil leaves the stripper 52 asthe bottom product through pipeline 62.

Water leaves the decanter or phase separation tank 36 through the pipeline 63 and passes to the methanol storage tank 16. The tar acids which are Withdrawn from the Y bottom of the phase separator tank 36 are substantially free of neutral hydrocarbons and pass through the pipeline 3S to the fractionating tower 43 where the tar acids are separated into two fractions. The fraction boiling below 230 C. leaves the top of the fractionating tower as distillate through a pipeline 64 and is conveyed to either storage or further processing facilities. Thetar acids boiling above 230 C. leave the fractionating tower 4t? as bottoms and pass through a pipeline 66 and enter a mixing tank 68.A Naphtha solvent is pumped through a Y pipeline '70 into the mixing tank 68 where it is mixed with the high boiling tar acids in a ratio of about onehalf Volume of naphtha solvent for each volume of tar acids. The naphtha solvent is mixed with the tar acids at this point to lower the viscosity of the tar acids prior to their entering a countercurrent extraction column 72. The tar acids and naphtha mixture is pumped through a pipeline 74 into the continuous countercurrent double solvent center feed extraction column 72. The'extraction column 72 is similar to the extraction column 14 and may beV of any convenient design capable of providing aY the desired separation of the color producing dihydricV phenols from the tar acids.

Aqueous methanol solution is fed continuously from the aqueous methanol storage tank 16 through a pipeline e into the top of the extraction column 72. A mixing valve 7S is positioned in the pipeline 76. Water is conducted through a pipeline into the mixing valve 78 Where it is mixed with the methanol from the methanol storage tank 16 so that the aqueous methanol solvent contains between 3G to 4t) percent by weight methanol. Naphtha is fed continuously from the naphtha storage tank 24 through a pipeline 82 into the bottom of the extraction column 72.

Since the aqueous methanol solution has a greater density than the naphtha, the aqueous methanol entering the extraction column 72 through the pipeline 76 will descend through the extraction column 72 and dissolve the color producing dihydric phenols while the naphtha solution passes countercurrently upward through aqueous methanol and naphtha solvents are four to sixV volumes of aqueous methanol and two to three volumes of naphtha for each volume of tar acids. It should be understood, however, when the tar acids are treated with naphtha before entering the extraction column, the ,rate of naphtha feed in the column will be proportionately decreased to maintain the preferred ratios.

The aqueous methanol extract containing the color producing dihydric phenols is withdrawn continuously from the bottom of the extraction column 72 through a pipeline 8d and fed into a distillation column |or stripper 86. ln the stripper S6 the methanol solvent is separated from the water and color producing dihydric phenols. The mixture of water and color producing dihydric phenols mixture leaves the stripper 36 as bottoms through a pipeline 8S for further treatment or storage.

Anhydrous methanol passes overhead from the stripper 36 through a pipeline 90 into a reflux condenser 92. The anhydrous methanol leaves the reflux condenser 92 through a pipeline 94 which conveys the anhydrous methanol to the aqueous methanol storage tank V16. The stripper 86 is provided with a reiiux pipeline 96 which is operable to return a portion of the condensed methanol to the stripper 86 as a reflux.

Naptha solvent containing de-pinked, dissolved tar acids leaves the top of the extraction column 72 through a pi eline 93 and passes to a distillation column or stripper 1%@ where the naphtha is separated from the depinked tar acids. per 1li@ as bottoms through a pipeline 162 and are pumped to storage or further processing facilities. The naphtha passes overhead from the stripper 109 through a pipeline 104i and enters a reflux condenser 166. The naphtha which leaves the redux condenser 106 enters a pipeline it-3 `and is conveyed tothe naphtha storage tank 24. A pipeline llt) is connected to the pipeline 106 and the stripper 191B and is operable to return a portion of the naphtha as reux for the stripper 160.V Y Y A tank 112 supplies Yadditional make-up methanol through the pipeline 114 to the aqueous methanol storage tank 16. Although the mixing valves 20 and 78 are shown diagrammatically, it should be understood that the valves 20 and '73 are the equivalent of any means operable The de-pinked tar acids leave the stripto regulate the concentration of the methanol solution so that ,the methanol .Solution will be cproper methanol concentration to etect separation in the respective extraction columns 14 and 72 EXMPLES TF6 illustrate the Present.Presesefslntity cifrar tiroducedv byv low temperature,.,carbonization of bituminous Coal ,Wes resented .and tsppedls. C .The topped tar was separatedintoa Viirstmfraction containing neutral oils. andl a `.second fraction containing-* tar acids by the process describe-*din 4I l. Si. Ratent2 66 6,796 above-mentioned. .T he resultingtar acids fraction was fractionated into a distillate containing l:tara cidsJboiling below 230 C.

and a 'second fraction ,containing {tar} acids boiling from 230 to 350. `,C.f,.sfo-calledy highboiling .tar acids.

These high boiling tar acids. were' subjected to a standard .pinkingtest to determine whether color producing dihydric phenols. were present. The test comprises mixing the tar acids With asolntion of 10% ,sodium hydroxide and then air blowing themixture.. After a short period of the. air blowing,.tar acids. which contain color produc- `ing dihydric phenolswilll` exhibit a characteristic pink color. The tar .acids used in .these examples. exhibited AAqueous methanol Asolr/'enLwa'sv fed intothetop .of the extraction column; a commercialhexane solventwas fed into the ,bottonnof the extraction columnandmaintained as, the ycontinuons phase. hllnfthe followingtablesf are tabulated v,processing conditions and results from these runs fol-,removing -thecoior producing dihydric phenols from high boiling 'tar acids.

Table A Concentration of aqueou methanol i 30% Feed rates (volumes):

Tar acids hexane mixture Aqueous methanol He am: v Yields (Wt. percent of tar acids in feed):

Aqueous methanol extract Hexane ralnate Ooi-i com To determine the pinkin'g properties of the tar acids En the` hexane raiinate,Y the hexanel wasfirstl removed by distillation. The remaining tar acids Were then selectively distilled andtractions boiling at 10 intervals were subjected to the pinliing test.

in run A Ythe tar acids from the hexane ranate boiling between 230 C. and 260 .C. did. not turn pinkwhen subjected to the pinkingtest whereas the tar acids boiling between 260 C. vand 350 C. did turn pink under the same testing conditions. The results of these tests on run A indicate that all of the color producing dihydric phenols are removed from the tar acids boiling between 230 C. and 260 C. when aqueous methanol having a concentration of 30 weight percent of methanol is used.

In run B the tar acids from the hexane ranate boiling between 230 C. rand 280 C. failed to turn pink when subjected to the pinliing test Whereas the tar acids boiling between 280 C. `and 350 C. did turn pink under the same testing conditions. rl`hese test results on run B indicate that all the color producing dihydric phenois are removed from the tar acids boiling vbetween 230 C. and 280 C. when aqueous methanol having ya concentration of 35 weight percent methanol is used.

ln run C the tar acids in the hexane rainate boiling 'the proper ,uitha oLcQnC subjected I0y the pinkinsfesfswhereaathe residue .boiling vmovedbyl .clistillation.. The Vremaining (tar. `acids Iwere 'selectively distilledfand subjected to the pinkingtests. 'In allo''thevr runs V,the 'tai'. acids lof the aqueousqrnethanol 'extract turned pink` l hen subjected to vthe pinking test, thus .indicatingfthepr ce of t he vcolor producing dihydric phendsiri4 q uequsmethanol extract.

Thus twillbes. elijaccorrlin'g to ,the above .tabl that color producingdihydric phenols can be vsepa'ratedfirom highboiling tarlacids byf'nieans of the present invention and that high'yields ofde-pi nke d tar acids' can` be obtained. i eld ofv tar acids inthe hexane nt and a cut ofY the tar4 acids boiling nd 260.,QCglf1a'st been completelydepinked. Injrun C idsffyieldis I7.9%;herrn/ever, in conjunction` slightly lower yield.a fraction oi.ta'r `ac ids ljoilingbetween 230 C. and 300 C. has beenffc'onpletel'y dp'k`d.

Thus there is' a :tivelycompIetede-pinking ofthe tar acids with the concentration of methanol at 40 weight Percent. ,The examples', also and it Ais des ed'tofdeV vtlgefta'i'f'2 1c i ds in 'this product K h N entrationfwouldbe 35% and the hexane rain'ate would contain 88% of theA tar acid f eedmixture. Ot this 88% allof'theV productlboiling Promising..,lhydrispliellols is shownin. run B- A Qserdiile ,t0 the.'-prsent'inventon; therefore, it .is now. possible:to extract? polo;- .producing dihydric. phenols from .high boiling acid'sand alSQit is .110W pcssibleto selectively extract color producin'g dihydricphenols from certain predeterminedfllts'rof high boiling tar. acids.

.According togthe vprovisions of the patent, statutes,.1 have explainedth principle; preferred construction land mode ofoperation olmyinvention and llaat/elillustrated and described whatl'now consider to representits best embodiment.' -However, Ifdesire to have it understood that, Withinthescope,ofthe appended claims, theinvention maybe practiced otherwise than as specically illustrated and described.

1. A process for extracting de-pinked tar v acids .from a tanacid oil fraction obtained from low temperature carbonization of bituminous vcoal which comprises the steps of. feeding`,. said taracid oil into a verticaly extraction zone, feeding a, s`olvent.consisting essentially of Yaparalnic n'aphtha'fraction boiling within the range of,60 to .130 .C. and lhaving a density of less than y0.8 .into the bottom pffsaidextraction zone, lfeeding a second solvent'co'nsisting essentially. oan aqueous methanol solution containing A55 to y75 Weight percent methanol and the balance water. into the top of said extraction zone, passing said naphtha through said extraction zone countercurrently to and in intimate contact with said aqueous methanol` solution, recovering an aqueous methanol ex- .tract containing tarracidswfrom the bottom of said vertical extractionzongpassing vsaid aqueous methanol extract into a first distillation zone, separating the methano 1 from the tar acids andwater in said rst distillatonzcne..recovengamixture of tar acids and water from said first distillation zone, recovering the tar acids from the mixture of tar acids andV water by phase separation, passing thus separated tar acids into a second distillation zone, recovering those high boilingtar acids boiling above 230 C. from said second distillation zone substantially free of neutral hydrocarbons, Vmixing said high boiling tar acids with paraflinic naphtha, feeding said treated high boiling tar acids into a second extraction zone, feeding a third solvent consisting essentially ofparainic naphtha having a density of 0.8 into the bottom of said second extraction zone, feeding a fourth solvent Yconsisting essentially of an aqueous methanol solution containing about 30 to 40 percent by weight methanol and the balance water into the top of said second extraction zone, passing said naphtha through said extraction zone countercurrently to and in intimate contact with said aqueous methanol solution, maintaining said third solvent as the continuous phase in said second extraction zone, regulating the ratios of said solvents to maintain a two liquid phase system within said extraction zone, and recovering a naphtha ratmate containing the de-pinked high boiling tar acids.

2. An extraction process for separating dihydric phenols from a mixture consisting essentially of monohydric phenols and dihydric phenols that boil above 230 C. which comprises feeding said mixture into an extrac-V tion zone, feeding a solvent consisting essentially of paraftinic naphtha having a density of less than 0.8 into said extractionzone, feeding a second solvent consisting essentially of an aqueous methanol solution containing about 30 to 40 percent by weight methanol and the balance water into said extraction zone, passing said naphtha through said extraction zonetcouutercurrently to and in intimate contact withV said aqueous methanol solution, regulating the ratios of Ysaid solvents to maintain a two liquid phase system Withinsaid extraction zone, and recovering an aqueous methanol extract containing dihydrio phenols and-a naphtha rainate from said extraction zone.

3. An extractionk process for-separatingY dihydric phei nols and monohydricphenols fromV aV mixture consisting essentially of monohydric phenols and V dihydric phenols .that boil. above 230 YC. which comprises mixing said mixture with paraffinic naphtha, feeding the treated mixture into a vertical countercurrent extraction zone, feeding a solvent consisting essentially of parainic'inaphtha having a density of less-.than 0.8 into the bottom of `said extraction zone, feedinga second solvent consisting essentially ofY an aqueous'rnethanol solution containing about 30 to 40 percentby weight-methanol and the balance water into the top of saidextraction zone, passing said naphtha through said'extractionfzone countercurrently to and in intimate contact with Vsaid aqueous methanol solution, regulating the ratios of said solvents to maintain a two liquid phase system within said extraction zone, and recovering an aqueous methanol extract containing dihydric phenols. t Y Y t 4. The process of claimY 3 in which theinaphtha is the continuous phase in said extraction zone.

' 5. An extraction process for separting dihydric phenols and rnonohydric phenols contained in a mixture consisting essentially of /monohydric phenols and dihydric phenols that boil above 230 AC., whichcomprises the steps of feeding said mixture into a vertical countercurrent extrac- 'tion zone, feeding a solvent consisting essentially of parafnic naphtha having a density of less than 0.8 intothe bottom of said extraction zone, feeding asecond solvent YconsistingV essentially of an aqueous methanolsolution containing 30 to 40 percentbyweight of methanolV and 'the balance water into the top of said extraction zone,

rpassing said naphtha through s aid extraction ,zone` counter- V`currently to 'and in intimate contact with said yaqueous Ymethanol solution, 'regulating the ratios of said'solvents ito maintain a two liquid phase systemV within said-extracntion zone, and'recov'ering aqueous Vmethanolextract containingrdihydric phenolsrfrom the bottom of said extraction zone.

6. An extraction process for separating dihydricphenols and monohydric phenols contained in a mixture of 5 high boiling phenols consisting essentially of monohydric phenols and dihydric phenols that boil above 230 C., .'hich comprises preparing a solution of said mixture in paraiinicY naphtha, feeding said solution into a` vertical countercurrent extraction'zone, feeding a solvent consistl0 ing essentially of paranic naphtha having a density of less than 0.8 into the bottom of said extraction zone, feeding a second solvent consisting essentially of an aqueous methanol solution containing 30 to 40 percent by weight methanol and the balance water into the top of said extraction zone, passing said naphtha through said extraction zone countercurrently to and in intimate contact with said aqueous metha-nol solution, regulating the ratios of said solvents to maintain a two liquid phase system within said extraction zone, and recovering an aqueous methano1 extract containing said dihydric phenols from the bottom of said Vertical extraction zone and a naphtha raffinate from the top of said vertical extraction zone.

7. The process of claim Y6 in which methanol is separated from the aqueous methanol extract by distillation and recirculated in said extraction zone and that portion of the aqueous methanol extract remaining after removal of the methanol is separately recovered and the naphtha Vis separated from the naphtha rafnate by distillation and recirculated in said extraction zone and that portion of the naphtha rainate remaining after removal of the naphtha is separately recovered. I 8. The process of claim 6 in which the naphtha solventis a hexane cut of petroleum naphtha.

9. An extraction process for separating the color pro- 'ducing dihydric phenols from a mixture consisting essentially of monohydric phenols and dihydric phenols obtained from a distillate fraction of the tar produced by the low temperature carbonization of bituminous coal, which ',comprises feeding that portion of said mixture of mon- 49 hydric phenols and dihydric phenols boiling above 230 C. into a vertical countercurrent extraction zone, feeding a solvent consisting essentially of parainic naphtha having a density of less than 0.8 into the bottom of said extraction zone, feeding a second solvent consisting essentially of an aqueous methanolrsolution containing 30 to 40 percent by weight of methanol and the balance water into the top of said extraction zone, passing said lnaphtha through said extraction zone countercurrently to and in intimate contact with-said aqueous methanol solu- 50 tion, regulating the ratios of said solvents to maintain a two liquid phase systemwithin said extraction zone, `'and recovering from said extraction zone an aqueous methanol extract containing the color producing dihydric Vphenols yand a naphtha solution containing monohydric 59 phenols.

l0. A selective extraction process forseparating color producing dihydric phenols and monohydric phenols, contained in a mixture of high boiling phenols consisting essentially of monohydric phenolsand dihydric phenols 50 that boil above 230 C, which comprises the steps of feeding said mixture into a vertical countercurrent extraction zone, feeding a solvent consistingV essentially of paralnic naphtha having a density of less than 0.8 into the Vbottom of said extraction zone, feeding a second solvent consisting of an aqueous methanol solution containing about 30 to 40 percent by weight of methanol and the balance water into the top of said extraction zone, passing said nap'natha through said extraction zone countercurrently to and in intimate contact with said aqueous methanol solution, regulating the ratios of saidv solvents to Vmaintain a two liquid phase system within said extraction zone, and recovering a naphtha ranate containing de-pinked phenols boiling between 230 C. and 260 C.' from the bottom of said extraction zone.

1l.` An extraction process for separating the color producing dihydric phenols from a mixture consisting essentially of monohydn'c phenols and dihydric phenols boiling above 230 C., which comprises the steps of feeding said mixture into a vertical countercurrent extraction zone, feeding a solvent consisting essentially of paranic naphtha having a density of less than 0.8 in to the bottom of said extraction zone, feeding a second solvent consisting essentially of an aqueous methanol solution containing about 35 to 40 percent by weight of methanol and the balance water into the top of said extraction zone, passing said naphtha through said extraction zone countercurrently to and in intimate contact with said aqueous methanol solution, regulating the ratios of said solvents to maintain a two liquid phase system within said extraction zone, and recovering a naphtha ra'nate containing de-pinked phenols boiling between 230 C. and 280 C. from the bottom of said extraction zone.

12. A method of extracting color producing phenolic constituents from high boiling tar acids consisting essentially of monohydric phenols and dihydric phenols that boil above 230 C. which comprises feeding the tar acids containing the color producing constituents into a vertical countercurrent extraction zone, feeding a solvent consisting essentially of parainic naphtha having a density of less than 0.8 into the bottom of said extraction zone, feeding a second solvent consisting essentially of an aqueous methanol solution containing about 30 to 40 percent by weight methanol and the balance water into the top of Said extraction zone, passing said naphtha through said extraction zone countercurrently to and in intimate contact with said aqueous methanol solution, regulating the ratios of said solvents to maintain a two liquid phase system within said extraction zone, and recovering a naphtha rainate from said extraction zone containing said tar acids free from color producing phenolic constituents.

13. A process for extracting de-pinked tar acids from a tar acid oil fraction obtained from low temperature carbonzation of bituminous coal which comprises the steps of feeding said tar acid oil into a vertical extraction zone,

feeding a solvent consisting essentially of a para'nic naphtha fraction boiling within the range of 60 to 130 C. and having a density of less than 0.8 into the bottom of said extraction zone, feeding a second solvent consisting essentially of an aqueous methanol solution containing to 75 weight percent methanol and the balance water into the top of said extraction zone, passing said naphtha through said extraction zone countercurrently to and in intimate contact with said aqueous methanol solution, recovering an aqueous methanol extract containing tar acids from the bottom of said vertical extraction zone, passing said aqueous methanol extract into a distillation zone, separating the methanol from the tar acids and water in said extraction zone, recovering the mixture of tar acids and water from the bottom of said distillation zone, recovering the tar acids from the mixture of tar acids and water by phase separation, passing said tar acids into a second distillation zone, recovering those high boiling tar acids boiling above 230 C. from the bottom of said second distillation zone substantially free of neutral hydrocarbons, feeding said treated high boiling tar acids into a second extraction zone, feeding a third solvent consisting essentially of parainic naphtha having a density of 0.8 into the bottom of said second extraction zone, feeding a fourth solvent consisting essentially of an aqueous methanol solution containing about 30 to 40 percent by weight methanol and the balance water into the top of said second extraction zone, passing said naphtha through said extraction zone countercurrently to and in intimate contact with said aqueous methanol solution, regulating the ratios of said solvents to maintain a two liquid phase system within said extraction zone, and recovering a naphtha raffinate containing the de-pinked high boiling tar acids.

Cotton Aug. 7, 1945 Gorin et al. Ian. 19, 1954 

1. A PROCESS FOR EXTRACTING DE-PINKED TAR ACIDS FROM A TAR ACID OIL FRACTION OBTAINED FROM LOW TEMPERATURE CARBONIZATION OF BITUMINOUS COAL WHICH COMPRISES THE STEPS OF FEEDING SAID TAR ACID OIL INTO A VERTICAL EXTRACTION ZONE, FEEDING A SOLVENT CONSISTING ESSENTIALLY OF A PARAFFINIC NAPHTHA FRACTION BOILING WITHIN THE RANGE OF 60* TO 130*C. AND HAVING A DENSITY OF LESS THAN 0.8 INTO THE BOTTOM OF SAID EXTRACTION ZONE, FEEDING A SECOND SOLVENT CONSISTING ESSENTIALLY OF AN AQUEOUS METHANOL SOLUTION CONTAINING 55 TO 75 WEIGHT PERCENT METHANOL AND THE BALANCE WATER INTO THE TOP OF SAID EXTRACTION ZONE, PASSING SAID NAPHTHA THROUGH SAID EXTRACTION ZONE COUNTERCURRENTLY TO AND IN INTIMATE CONTACT WITH SAID AQUEOUS METHANOL SOLUTION, RECOVERING AN AQUEOUS METHANOL EXTRACTED CONTAINING TAR ACIDS FROM THE OF SAID VERTICAL EXTRACTION ZONE, PASSING SAID AQUEOUS METHANOL EXTRACTED INTO A FIRST DISTILLATION ZONE, SEPARATING THE METHANOL FROM THE TAR ACIDS AND WATER IN SAID FIRST DISTILLATION ZONE, RECOVERING A MIXTURE OF TAR ACIDS AND WATER FROM SAID FIRST DISTILLATION ZONE, RECOVERING THE TAR ACIDS FROM THE MIXTURE OF TAR ACIDS AND WATER BY PHASE SEPARATION, PASSING THUS SEPARATED TAR ACIDS INTO A SECOND DISTILLATION ZONE, RECOVERING THOSE HIGH BOILING TAR ACIDS BOILING ABOVE 230*C. FROM SAID SECOND DISTILLATION ZONE SUBSTANTIALLY FREE OF NEUTRAL HYDROCARBONS, MIXING SAID HIGH BOILING TAR ACIDS WITH PARAFFINIC NAPHTHA, FEEDING SAID TREATED HIGH BOILING TAR ACIDS INTOA SECOND EXTRACTION ZONE, FEEDING A THIRD SOLVENT CONSISTING ESSENTIALLY OF PARAFFINIC NAPHTHA HAVING A DENSISTY OF 0.8 INTO THE BOTTOM OF SAID SECOND EXTRACTION ZONE, FEEDING A FOURTH SOLVENT CONSISTING ESSENTIALLY OF AN AQUEOUS METHANOL SOLUTION CONTAINING ABOUT 30 TO 40 PERCENT BY WEIGHT METHANOL AND THE BALANCE WATER INTO THE TOP OF SAID SECOND EXTRACTION ZONE, PASSING SAID NAPHTHA THROUGH SAID EXTRACTION ZONE COUNTERCURRENTLY TO AND IN INTIMATE CONTACT WITH SAID AQUEOUS METHANOL SOLUTION, MAINTAINING SAID THIRD SOLVENT AS THE CONTINUOUS PHASE IN SAID SECOND EXTRACTION ZONE, REGULATING THE RATIOS OF SAID SOLVENTS TO MAINTAIN A TWO LIQUID PHASE SYSTEM WITHIN SAID EXTRACTION ZONE, AND RECOVERING A NAPHTHA RAFFINATE CONTAINING THE DE-PINKED HIGH BOILING TAR ACIDS. 